Parameter

Event handler which is run every time an HTTPS Callable function URL is hit. The function is called with data passed from the client. The value returned from this handler, either as a Promise or returned directly,
is sent back to the client. If this handler throws (or returns a rejected Promise with) an instance of HttpsError, then the error details are sent back to
the client. If this handler throws any other kind of error, then the client receives an error of type INTERNAL.